Laufey Regio: A newly discovered topographic rise on Venus

Abstract

[1] Laufey Regio is a 0.5 km high, elongate topographic rise, measuring 1000 by 2000 km, located within northern Navka Planitia, Venus. It is dominated by two large volcanoes, Var and Atanua Montes, and numerous coronae with associated flow deposits. The area has been geologically mapped, showing that large-scale edifice formation focused at Var and Atanua Montes and overlapped in time with the formation of smaller coronae. Several coronae and volcanoes have had complex and protracted histories with multiple episodes of volcanism and tectonism, supporting a nondirectional history for this region. The broad topography of the rise is surrounded by a concentric set of wrinkle ridges interpreted to have formed after the onset of centralized volcanism. Admittance studies indicate both bottom and top loading, but lithospheric parameters are not well constrained. Top-loading models give a range of 0-48 km for elastic thickness (T e ) and 35-115 km for crustal thickness. We interpret the T e range as most likely indicating isostatic compensation. Bottom-loading models yield lower bounds of 30-75 km for T e and 32-74 km for the apparent depth of compensation (ADC). The combination of the large T e and low topography indicates that the plume is no longer active. Bottom loading and a small ADC may indicate that a layer of low-density residuum, produced by pressure release melting in the now extinct plume, is partially supporting the topography. On the basis of its broad, regional topography, abundant volcanism, and gravity signature, we interpret Laufey to be a volcano-dominated rise in a late stage of evolution. INDEX

Gravity analysis of Parga and Hecate chasmata: Implications for rift and corona formation

“…The average Z L value we obtain for classes interpreted using a bottom‐loading model is 79 km and ranges from 32 to 152 km. Some variation in Z L may be due to the range of dynamic processes in chasma formation, but the range is similar to those obtained in previous studies of other geological structures [ Brian et al , 2004; Herrick et al , 2005; Anderson and Smrekar , 2006; Grindrod et al , 2006]. Smaller values of Z L of less than 50–75 km are probably best interpreted as crustal thickness.…”

Global mapping of crustal and lithospheric thickness on Venus

“…For those regions where the elastic thickness is low, the overall signature is consistent with a plume at depth. Rises with larger T e values likely are inactive, as previously proposed for Bell [ Smrekar , 1994] and Laufey [ Brian et al , 2004]. In these areas the bottom loading may not be dynamically compensated by a plume but instead underlain by broad regions of depleted mantle resulting from pressure release melting.…”

“…Atla, Bell, Themis, and Western, Eastern, and Central Eistla regions have both a short‐wavelength top load and a long‐wavelength bottom load, interpreted as being due to volcanoes and mantle plumes, respectively [ Phillips , 1994; Smrekar , 1994; Smrekar et al , 1997; Smrekar and Stofan , 1999]. Laufey Regio is a newly examined region that is interpreted as an extinct hotpot on the basis of its relatively large elastic thickness and small apparent depth of compensation [ Brian et al , 2004].…”

Distribution of Eruptive Centers on Top of Large Shield Volcanoes in the Inner Solar System: General Classification and Glimpses of Their Subvolcanic Structure

“…The volcano has a diameter of 1,000 km, and it is formed by three main cones with heights from west to east of 1.5, 0.7, and 1.7 km. The flank slopes vary from 0.14° to 2° (Brian et al., 2004). The volcano has 88 volcanic vents, consisting of cones and small shields.…”

“…Most of the shield is constructed by flows that extend 500 km on average from the center of the volcano. Structurally, the volcano shows two groups of fractures: a group with west‐northwest (WNW) orientation to the west and another with east‐southeast (ESE) orientation to the east (Brian et al., 2004; Herrick et al., 2005).…”